3GPP Network Architecture Radio Access Technologies Discussion

UMTS vs. LTE: a comparison overviewUnik4230: Mobile Communications

Khai Vuong

May 16, 2011

3GPP Network Architecture Radio Access Technologies Discussion

Agenda

3GPP

Network ArchitectureUMTSLTE

Radio Access TechnologiesWCDMAOFDMA

Discussion

3GPP Network Architecture Radio Access Technologies Discussion

3GPP Standards (I) 1

3GPP: 3rd Generation Partnership Project

Version Released Info

Release 98 1998 specified pre-3G GSM network

Release 99 2000 Q1 specified the first version of UMTS, in-corporating a CDMA air interface

Release 4 2001 Q2 aka. Release 2000, added all-IP CoreNetwork

Release 5 2002 Q1 introduced IMS and HSDPA

Release 6 2004 Q4 integrated operation with Wireless LANnetworks and added HSUPA, MBMS,enhancements to IMS

1http://en.wikipedia.org/wiki/3GPP

3GPP Network Architecture Radio Access Technologies Discussion

3GPP Standards (II) 2

Version Released Info

Release 7 2007 Q4 decreasing latency, improvementsto QoS and real-time applications,HSPA+ , NFC, EDGE Evolution.

Release 8 2008 Q4 First LTE release. All-IP Network(SAE), new OFDMA, FDE and MIMObased radio interface.

Release 9 2009 Q4 SAES Enhancements, Wimax andLTE/UMTS Interoperability

Release 10 2011 Q1 LTE advanced

2http://en.wikipedia.org/wiki/3GPP

3GPP Network Architecture Radio Access Technologies Discussion

3GPP data evolution 3

3Huawei Technologies Co., Ltd. 2009

3GPP Network Architecture Radio Access Technologies Discussion

User experience

Type of services UMTS LTE

Web surfing 8 seconds immediately

Download 5MB music 3 minutes 1 second

Download 750MB movie 6.5 hours 2.5 minutes

Download HD video ∼2-3 days ∼15 minutes

Video telephony√ √

Corporate VPN, Intranet√ √

Mobile TV√ √

On-demand TV√

Video-based mobile advertising√

...√

Table: Data services4

4Huawei Technologies Co., Ltd. 2009

3GPP Network Architecture Radio Access Technologies Discussion

Services for telecommunication systems

1. Teleservice: Information that transfered between end users,e.g speech service, messaging, emergency calls.

2. Bearer service: Different QoS classes for various type oftraffic:

• Conversasional: voice, video, telephony, video gaming• Streaming: multimedia, video on-demand, webcast• Interactive: web browsing, network gaming, database access• Background: email, SMS, downloading

3GPP Network Architecture Radio Access Technologies Discussion

UMTS objectives

1. improvement in data performance, multimedia services andaccess to the Internet

2. new radio interface WCDMA

3. Core Network: connection function

3GPP Network Architecture Radio Access Technologies Discussion

Core Network for UMTS

• MSC:Mobile switching center, switch the CS transactions

• GMSC: Gateway MSC: a switch that connects the UMTS PLMN to the externalCS networks.

• SGSN: Serving GPRS Support Node, similar to MSC/VLR but this is for PStraffic.

• GGSN: Gateway GPRS Support Node, similar to GMSC but it serves for the PStraffic.

3GPP Network Architecture Radio Access Technologies Discussion

LTE’s objectives 5

1. higher data rates in both downlink and uplink transmission

2. reduce packet latency, more responsive user experience

3. flat architecture: IP-based, open interfaces, simplified network

4. flexible radio planning and high spectral efficiency

5. reduce delivery costs for rich communications

6. long-term revenue stability and growth

7. coexistence alongside circuit switched networks

5UMTS Forum 2008

3GPP Network Architecture Radio Access Technologies Discussion

Why LTE?6

Non-3GPP technologies

GSM EDGE WCDMA HSPA LTE

Figure: Flexible upgrade path

Figure: Reduce pris per MB toremain profitable

6Nokia Siemens Networks

3GPP Network Architecture Radio Access Technologies Discussion

UMTS vs. LTE Architecture

Figure: Network architecture, simplified 7

LTE: simplified IP flat architecture• BSC/RNC disappeared, functions transfer to eNodeB

• All eNodeB connect directly through X2 interface

• PS service only, voice over IP.7Image courtesy: UMTS Forum 2008

3GPP Network Architecture Radio Access Technologies Discussion

LTE’s interfaces: S1 and X2 8

• S1: self-optimizing network

• X2: connects eNodeB

• MME (MobilityManagement Entity):distribution of pagingmessage to eNodeB

• UPE (User Plan Entity): IPheader compression,encryption of user datastream, termimating andswitching of U-plane

8Image courtesy: developer.att.com

3GPP Network Architecture Radio Access Technologies Discussion

Wideband CDMA

Figure: Access technique for UMTS 9

9Huawei Technologies Co., Ltd. 2009

3GPP Network Architecture Radio Access Technologies Discussion

CDMA: Principles

• each user is assigned a spreading code for encoding it’s data

• Receiver knows the code of user, it can decode the receivedsignal, recover the original data

• Bandwidth of coded data signal much larger than originaldata signal due to the encoding process spreads the spectrumof the origianl signal, based on spread-spectrum modulation

3GPP Network Architecture Radio Access Technologies Discussion

WCDMA in UMTS [4]

• Direct Sequence CDMA system, with chip-rate 3.84 Mc/s

• Combined with FDMA: every carrier is allocated 5 MHzfrequency band so that many operators can provide serviceswithout interference each other.

• Codes: scrambling and channelization

Channelization: seperatestraffic to and from differentusers, called Orthogonal

Variable Spreading Factor

(OVSF) which varies from 1to 128

Scrambling codes: notincrease bandwidth, but isused for distinguishingterminals in uplink andsectors (cells) in downlink

3GPP Network Architecture Radio Access Technologies Discussion

LTE’s downlink: OFDMA

OFDM: Multiple access scheme,allows simultaneous connectionsto/from multiple mobileterminalsUsers share different subcarriers,either consecutive or distributedmanner.

3GPP Network Architecture Radio Access Technologies Discussion

LTE’s uplink: Single Carrier-FDMA

• SC-FDMA: hybrid modulationscheme that combines the lowPAPR techniques of single-carriertransmission systems, such as GSMand CDMA, with the multi-pathresistance and flexible frequencyallocation of OFDMA

• Data symbols in the time domainare converted to the frequencydomain using a discrete Fouriertransform (DFT)

• Cyclic Prefix (CP) is added, a serialsequence of symbols is modulatedand transmitted instead of parallelOFDM-scheme

• On receiver’s side, an extra N-pointIDFT is applied to reconstruct theoriginal symbols.

Figure: Structure for UL and DL inLTE [5]

An advantage of SC-FDMA compares toOFDMA is low Peak to Power Average

Ratio (PAPR), that helps increasingbattery life.

3GPP Network Architecture Radio Access Technologies Discussion

References

Ville Eerola, LTE Network Architecture Evolution, Lecturenote in T-109.5410 Technology Management in the

Telecommunications Industry, Helsinski University ofTechnology, 2010.

UMTS Forum, Toward Global Mobile Broadband, retreivedMay 16, 2011fromwww.umts-forum.org/component/option,com.../Itemid,12/

M. Neruda and R. Bestak, Evolution of 3GPP Core Network,IWSSIP 2008.

Lecture notes in UniK 4230, UiO, Lecture9-10.pdf

OFDM(A) for wireless communications, Telenor R&I R 7/2008

3GPP Network Architecture Radio Access Technologies Discussion

A brief comparision 10

Requirements UMTS LTE

Spectral Efficiency 0.2bit/s/Hz 1.57bit/s/Hz

Peak Data Rate 2 Mbit/s 170 Mbit/s

Sector Capacity 1 Mbit/s 31.4 Mbit/s

No. of Tranceivers/Cell 30 1

RTT User Plane 50 ms 5 ms

Call setup time 2 s 50 ms

Mobility 250 km/h 350 km/h

Bandwidth 5 MHz scalable up to 20 MHz

10UMTS/HSPA to LTE Migration, Motorola Inc. 2009

3GPP Network Architecture Radio Access Technologies Discussion

Discussion

Point to discuss, focus on this topic, futher questions?